Electronic blast control system for multiple downhole operations

ABSTRACT

A system for multiple subsurface operations which are carried out in a well bore by means of two or more well tools having explosive or gas generating charges which are electronically initiated for accomplishing any number of other downhole well activities. Two or more well service tools are simultaneously run into a well on a single wire-line and are located at predetermined positions. An electronic blast control system having safety parameters, including time, movement, pressure and the like to ensure safe running and independent firing of the tools. The blast control system permits controlled energization of the explosive charges only when all of the programmed parameters have been met and causes sequential or serial electronic firing of the explosive devices independently of one another by positive and negative voltages.

RELATED PROVISIONAL APPLICATION

Applicant hereby claims the benefit of U.S. Provisional PatentApplication No. 61/399,091 filed on Jul. 7, 2010 by Otis R. Anderson andentitled “Electronic Blast Control System For Multiple DownholeOperations”, which Provisional Patent Application is incorporated byreference herein for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to subsurface operations which arecarried out in a well bore by means of one or more spaced explosivecharges which are typically contained within spaced blast joints orblast guns and are electronically initiated for doing such work asperforation of well casing by means of shaped charges, setting ofpackers by means of explosive generated pressure, and for sequentiallyaccomplishing any number of other downhole well activities. Morespecifically, the present invention concerns a method and apparatus forelectronically controlling well service operations for two or more wellservice tools that are simultaneously run on a wire-line to ensure safeand timely sequential or serial operations such as casing perforation.Even more specifically, the present invention concerns safelypositioning explosive type well tools at selected predetermined depthswithin a well bore or well casing and safely and sequentiallyelectronically firing the explosive devices independently of one anotherto achieve the intended work. The present invention concerns the use ofa positive voltage for controlling firing of one typically lower welltool and negative voltage for controlling firing of an adjacent,typically upper well tool so that the firing of a well tool will notcause unintentional firing of or damage to another well tool.

2. Description of the Prior Art

Since the handling of explosives is an inherently dangerous activity,for the protection of personnel and equipment from the adverse effectsof undesired explosive detonation it is highly desirable to provide afiring control system that permits firing of the explosive charges of asingle perforating gun or those of two or more spaced perforating gunsonly under strictly controlled circumstances. It is imperative that adownhole explosive device be permitted to fire only when it is properlylocated at designed depth within the well; otherwise, the well casingcould be perforated at the wrong depths or well service personnel couldexperience significant danger.

Electronic blast control systems have been developed for actuation ofexplosive charges within wells for doing work, such as perforation ofwell casing, setting of packers and various other downhole activitiesrequiring significant energy. Some electronic blast control systems areinitiated from the surface via an electric line for electrical supplyand control. Other electronic blast control systems are conveyed onwire-line and employ battery power and electrical charge pumping toconvert battery voltage, such as 12 volts to a charge firing voltage onthe order of 200 volts. Though blast control systems having electricline supply and control are used, such systems are quite expensive anddifficult because of the necessity for providing electrical supply andcontrol lines extending from the surface to the depth for the downholeactivity, which is typically near the bottom of the well. It istherefore desirable to provide a novel electronic wire-line conveyedblast control system that ensures that a downhole explosive device whichfails to fire or is not fired for any number of reasons can beefficiently and safely retrieved from the downhole environment withoutcompromising the safety of the well equipment or the well personnel atthe surface.

More recently, electronic blast control systems have been developed foractuation of explosive charges within wells for doing work, such asperforation of well casing, setting of packers and various otherdownhole activities requiring significant energy. Some electronic blastcontrol systems are initiated from the surface via an electric line forelectrical supply and control. Other electronic blast control systemsare conveyed on wire-line and employ battery power and electrical chargepumping to convert battery voltage, such as 12 volts to a charge firingvoltage on the order of 200 volts. Though blast control systems havingelectric line supply and control are used, such systems are quiteexpensive and difficult because of the necessity for providingelectrical supply and control lines extending from the surface to thedepth for the downhole activity, which is typically near the bottom ofthe well. It is therefore desirable to provide a novel electronicwire-line conveyed blast control system that ensures that a downholeexplosive device which fails to fire or is not fired for any number ofreasons can be efficiently and safely retrieved from the downholeenvironment without compromising the safety of the well equipment or thewell personnel at the surface.

Under circumstances where a wellbore intersects two or more productionzones it is typically necessary to perforate the well casing at each ofthe zones. According to present practices it is necessary toindependently run a perforating gun into the well for each zone. Aperforating gun is run into the well by wireline and is typicallylocated at the bottom production zone. The perforating gun is thenfired, preferably according to the method and using the apparatus thatis set forth in U.S. Pat. No. 5,369,579 of Otis R. Anderson. After thefirst perforating job has been completed, another perforating gun isthen run into the well by wireline and is positioned at a productionzone that is above the lower production zone and is electronicallyinitiated in similar fashion. This process is continued for as manyproduction zones as are intersected by the wellbore. Independentlyrunning a number of well tools into a well in this fashion is anexpensive proposition due to the significant rig time and labor coststhat are involved. It is desirable therefore, to provide for running aplurality of well tools into a well with a single tool running operationand then initiating the well tools sequentially, while at the same timeprotecting the well tools against inadvertent simultaneous initiation.

SUMMARY OF THE INVENTION

The subject matter of the present invention is directed generally toblast control systems for perforating guns that are employed toperforate well casing at the depths of two or more production formationsor zones that are intersected by the wellbore. This electronic blastcontrol system is controllable so as to safely permit sequential orserial firing of casing perforation charges or other sequentialelectronically activated events at different formation depths within awell. However, it is understood that the present invention concerns thecontrolled activation or firing of explosive or gas-generating chargesin the downhole environment for the performance of a variety of toolactivations, including setting or releasing packers or anchors or toactuate other mechanical or electromechanical devices. The term “blastcontrol”, as specified in this invention disclosure, is therefore notintended to limit the spirit and scope of the present invention to anyparticular downhole service activity, but rather is employed to indicatethe activation of sequential or serial downhole activities that arecontrolled by an on-board programmable electronic memory.

It is a principal feature of the present invention to provide a novelblast control system that is capable of selectively and sequentiallyactivating or firing two or more well service tools that aresimultaneously run into a well by a single tool conveying system such asa wire-line tool conveyor, a coiled tubing tool conveyor, a conduit typetool conveyor or any other conveyance system that is in use at thepresent time.

It is another feature of the present invention to provide a novel blastcontrol system for a plurality of well service tools, such as casingperforation guns, whereby the tools are run into the well or wall casingin an un-armed state and the arming and firing of an initial wellservice tool accomplishes arming and subsequent firing of a sequentialwell service tool, and so on until all of the well service tools havebeen individually fired and firing success has been confirmed.

It is also a feature of the present invention to provide a novel blastcontrol system having an electrical power supply including a storagebattery and processing circuitry for providing positive and negativefiring voltage that is selectively connected with individual detonatorsor other apparatus so that adjacent well service tools cannot be firedsimultaneously or out of sequence by any particular voltage.

It is another feature of the present invention to provide a novel blastcontrol system for multiple well service tools that require the firingof one well service tool to accomplish arming of another well servicetool before that tool can be fired under the control of the blastcontrol system.

Briefly, the various objects and features of the present invention arerealized through the provision of U.S. Pat. No. 5,369,579 of Otis R.Anderson is incorporated by reference herein for all purposes. Many ofthe features of the '179 patent will be employed together with thefeatures of the present invention to provide a multi-shot downhole wellservicing operation wherein two or more tools are run into a well casingsimultaneously by wireline equipment, typically known as “slick line”and are activated sequentially. This blast control system is primarilydesigned for serial energization or firing of spaced series relatedperforating guns; however it is not intended that the present inventionbe limited solely to perforating guns. Other downhole activities inwells, such as setting packers and anchors or cutting well casing canalso be performed in a manner that takes advantage of running tools intoa well a single time for the conduct of multiple downhole activitiesthat utilize explosive generated gas pressure or explosive actuation ofcomponents. When the multi-shot tools are in the form of casingperforation guns each having multiple shaped charges, the perforationguns are run into the well in the same run and are each positioned at adesigned depth. The perforation guns are activated responsive to voltageof designed polarity, positive or negative, and adjacent perforationguns or other well service tools are responsive to voltage of theopposite polarity. The reversed polarity voltage is achieved byreversing circuit diodes that permit the flow of boosted battery powerfrom a battery supply that is on board the instrument or tool of theblast control system. Obviously, in the case of wells, the first tool ofa spaced series of tools will be actuated by voltage of a selectedpolarity, positive or negative. The next succeeding tool will beactuated by voltage of opposite polarity, negative or positive, thusensuring against detonation or energization of adjacent well servicetools.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the preferred embodimentthereof which is illustrated in the appended drawings, which drawingsare incorporated as a part hereof.

It is to be noted however, that the appended drawings illustrate only atypical embodiment of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

In the Drawings:

FIG. 1 is a partial sectional view of a well intersecting threeproduction formations and showing three well tools, such as perforatingguns, being located in relation with the depths of the production zonesby a single wireline during a single run of a plurality of well servicetools;

FIG. 2 is a partial sectional view showing a multi-shot well servicetool for sequential actuation or firing of the well service tools ofFIG. 1;

FIG. 3 is a block diagram electronic schematic illustration showing thevarious electronic components of the multi-shot well service tool ofFIGS. 1 and 2;

FIG. 4 is a partial electronic schematic illustration showing the use ofpositive and negative amplified voltage for sequentially firing the wellservice tools of FIG. 1; and

FIG. 5 is a graphical illustration of a timing sequence and runningmotion pattern of ten minutes that is employed to establish parametersthat must be met for well service tool activation according to theprinciples of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The term “blast control” as used herein is intended to mean a controlsystem for two or more electronically initiated and sequentiallyactivated devices that develop an explosive force or rapid generation ofcombustion gas in the downhole environment for the purpose of doingdesired work. The work may take the form of casing perforation bysequential or series explosive shaped charges that develop specificallyoriented hot gas jets for perforation of well casing or make take theform of packers, anchors and the like which are activated to setpositions by explosive generation of gas.

Referring now to the drawings and first to FIG. 1, a well for productionof petroleum products such as crude oil and natural gas is showngenerally at 10 and incorporates a well casing 12 that lines a boreholeintersecting a plurality of subsurface production formations 14, 16 and18. The well casing is connected with a wellhead 19 which extends abovethe surface “S”. Though not shown, a wireline service mechanism having awireline lubricator will be mounted to the wellhead in conventional tocause controlled wireline running of the tools and to ensure sealing ofthe wireline against undesired pressure release as the wireline entersthe wellhead and casing. To complete the well for production of fluidsfrom the subsurface formation it is necessary to perforate the wellcasing at each production formation level to permit the well fluids toflow from the formations into the casing via the casing perforations.

While perforating guns are well service tools that are used forcompletion of most wells it is not intended to limit the spirit andscope of the present invention to perforating guns, it being understoodthat other downhole well service tools, such as packers, anchors, andother equipment may be run into a well casing together and selectivelyactuated in sequential manner via the use of the method and/or apparatusof the present invention. As mentioned above, perforation of well casingfor completion of multiple subsurface production zones typicallyrequires multiple service tool runs, one for each perforating gun,because explosive firing of a perforating gun might cause prematurefiring of another perforating gun. Though individual running of severalperforating guns is an expensive and time consuming proposition, for thesake of safety in almost every case each perforating gun is run,positioned at a desired formation depth and is fired for casingperforation. Typically the first of the perforating guns is fired at thelowermost formation depth and subsequent perforating guns are locatedand fired at the next higher formation depth since firing a perforatinggun can leave obstructions within the casing that might interfere withthe running of well service tools to deeper depths.

According to the method and using the apparatus of the present inventiontwo or more well service tools, such as casing perforating guns are runsimultaneously by a single wireline running tool and are individuallylocated at desired formation depths within the casing. The perforatingguns will not be permitted to fire until a complete set of parametershave been met, as discussed below. When explosive charge firingparameters have been met, only the lowermost perforating gun will bepermitted to fire and its firing is necessary to arm the nextperforating gun above, before that gun will be permitted to fire. Firingof the second well service tool causes arming of the third well servicetool, thus enabling the third well service tool to be fired, and so onuntil all of the well service tools have been sequentially fired.

As shown in FIG. 1 three well service tools, perforating guns “A”, “B”and “C” have been located at lower, intermediate and upper productionformation depths by a single wireline 20 via a single wireline runningtool 22. Each of the perforating guns is provided with a plurality ofspaced and strategically oriented shaped perforating charges ofexplosive composition that, when fired, will develop a concentrated hightemperature explosive jet that will penetrate the well casing and thesurrounding cement and in most cases penetrate a short distance into theproduction formation. The perforating guns will be fired sequentially,starting with the lowermost gun A. Firing of perforating gun A willgenerate a pressure pulse within the casing that will be detected andcause arming of perforating gun B but will not arm perforating gun C,which remains disabled or un-armed so that it cannot be firedsimultaneously with or before the charges of perforating gun B is fired.Subsequent firing of perforating gun B will arm perforating gun C sothat perforating gun C will then be capable of firing assuming itsfiring safety parameters have all been met.

The general firing parameters for safe conveyance, positioning andfiring of perforating guns and other well service tools are set forth isU.S. Pat. No. 5,369,579 of Otis R. Anderson. Subsequent firing ofperforating gun B will arm perforating gun C so that perforating gun Cwill then be capable of firing assuming all of its firing parametershave all been met.

With reference to FIGS. 2 and 3, an electronic blast control systemincorporating the features of this invention is illustrated generally at24 and incorporates an elongate instrument body shown generally at 26having an upper housing sub 28 within which is located a battery 30. Theupper housing sub 28 is provided with a threaded upper connection member32 which is adapted for connection of the blast control instrument to aconventional wireline running tool to thus enable the instrument 24 tobe run into a well bore and positioned at a predetermined depth withinthe well for sequential blasting or tool actuating operations. The upperhousing sub 28 also includes an externally threaded downwardly extendingconnector projection 34 to enable its physical and electronic couplingwith other electronic components of the blast control system orinstrument 24.

The housing structure of the instrument 24 also includes an intermediatepressure housing section 36 which is coupled and sealed in relation withthe upper housing sub and which is also coupled and sealed in relationwith the uppermost one of one or more detonator blast joints containinga plurality of spaced detonators 38A, 38B and 38C which are selectivelyelectrically initiated by means of electrical current from the storagebattery 30 under circumstances where multiple safe parameters of theblast control have been met so that electrical initiation of thedetonator is permitted. The detonators, upon selective sequential orserial initiation, will then achieve detonation of one or more shapedexplosive perforating or gas generating charges that are containedwithin the blast joint or joints for achieving the explosive initiateddownhole work that is desired.

The pressure containing housing 36 defines an internal chamber 40 havingtherein a plurality of electronic control modules which sense programmedwell conditions such as fluid temperature and hydrostatic pressure,which sense the motion of the instrument as it traverses the well boreor well casing while being inserted into or removed from the well andwhich provides a predetermined timed sequence within which the downholeblasting operation is permitted to occur. These pressure, temperatureand motion sensors and a clock timer provide electronic logic pulseswhich define safe and unsafe parameters for downhole blastingoperations. These electronic logic signals are input to a centralprocessing unit 42 having a microprocessor providing a firing signaloutput which controls battery current energization of the detonatorcircuit for electronic initiation of the detonator. The detonator willthen initiate the explosive charge or charges which are typically firstorder explosive devices but which may comprise any other suitableexplosive device for the work that is intended.

In preparation for downhole blasting activities, the blasting device ishandled during transportation to the well site and is then handled bywell personnel in preparation for its introduction into the well bore.After it is introduced into the well bore, typically by means ofconventional wireline equipment, it must be run through the well bore tothe designed depth for explosive detonation and must be secured relativeto the well casing prior to detonation. During handling and running ofthe downhole blasting tool, it is critical that explosive detonation notoccur.

It is also desirable that explosive detonation occur only when theblasting tool has accurately performed. For these reasons, according tothe teachings of the present invention, the electronic blast controlsystem of the present invention is provided with a plurality of sensorsand a clock timer that each provide an output of logic signalsreflecting sensed conditions. These logic output signals are conductedto the CPU 42 and are processed thereby. When predetermined logic outputsignals are received by the CPU, its signal processing will yield a CPUoutput signal causing battery current to be placed across the detonatorcircuit thereby initiating the detonator and inducing controlledblasting activity. If the output signals of the clock timer or any ofthe well condition sensors are not in accordance with predeterminedprogrammed conditions that are necessary for blasting activity, CPUprocessing of the signals will yield a logic output signal that preventsdetonator circuit energization by the battery section of the tool. Theelectronic blast control system includes a motion sensor circuit 44which detects any movement of the tool as it is being handled at thesurface and run into the well bore. The motion sensor also detectsmovement of the tool as it is being extracted from the well bore underconditions where, for any of a number of reasons, detonation will nothave occurred. The motion sensor circuit includes a timing sequencewhich is initiated each time motion of the tool ceases within the wellbore. A timing sequence of any suitable duration may be employed whichis suitable to the user. Thus, if the tool becomes temporarily stuckwithin the well bore during running and thereby becomes motionless,since it is not located at its designed depth for detonation, the motionsensor circuit will not yield a logic signal permitting firing of thedetonator until the timing sequence period has completed. Thus, shouldthe tool become stuck within the well casing during running, the timingsequence will become reset. Accordingly, before the detonator can befired, the timing sequence of the motion sensor must have run its courseand remain stable for a period exceeding the duration of the timingsequence.

It is desirable that the downhole blasting system be capable ofdetonating only during a predetermined period of time. It is necessarythat initiation of the detonator not occur until a predetermined timethat is sufficiently far in advance so that the blasting tool can beproperly positioned at its designed depth and proper orientation withinthe well casing. It is also desirable that there be a capability ofpre-setting a timed period during which detonator initiation can occurand before which and after which initiation of the detonator cannotoccur. Thus, if the detonators and their various associated apparatushas remained downhole for a period that is sufficiently long to exceed apredetermined time duration, for example, two hours, then it isdesirable to safely prevent initiation of the detonator, therebyenabling the electronic blast control system together with thedetonators and blast joints to be removed from the well. To accomplishthis feature, a clock timer circuit 46 is provided within the pressurecontaining chamber 40 of the pressure containing housing 36. The clocktimer circuit 46 derives its electrical energy from the battery 30 andprovides a logic output signal having a predetermined logic state whenthe clock timer circuit is within the predetermined firing period and anopposite logic state when the clock timer circuit is registering a timethat is either before or after the predetermined firing period. Thelogic output signals of the clock timer circuit are transmitted to theCPU for processing so that the firing signal that is output by the CPUcan occur only when the timing sequence is within the firing period thatis set or programmed at the surface by operating personnel.

In the downhole environment the well casing will contain a level ofdrilling fluid or completion fluid which will develop hydrostaticpressure within the well casing that is directly responsive at which thedepth at which the hydrostatic pressure is taken. Obviously, hydrostaticpressure at any predetermined depth within the well casing can be quiteaccurately identified. As an additional safety feature, the electronicblast control system of the present invention, shown by way of elevationin FIG. 2 and shown schematically in FIG. 3, is provided with a pressuresensor circuit 48 which is energized by the battery 30 and which senseshydrostatic pressure to which the blast control system is subjected. Thepressure sensor circuit 48 provides an electronic logic outputreflecting the hydrostatic pressure to which the tool is subjected atany point in time. This logic output is conducted to the CPU whichprocesses these signals along with other logic signals.

The circuit is capable of being pre-set or programmed to a predeterminedhydrostatic pressure range such that when hydrostatic pressure is withinthe predetermined range, such that when hydrostatic pressure is withinthe predetermined range a firing signal can be output by the CPU. If thehydrostatic pressure being sensed is outside the predetermined range,then the logic signal being received by the CPU will be such that theCPU cannot provide a firing signal, but rather, will provide a “safe”signal preventing initiation of either of the detonators 38A-38C byelectrical energy from the battery 30. Thus, well servicing personnelwill set the predetermined firing pressure range of the pressure sensorfor a rather narrow range of hydrostatic pressure that is calculated tobe present at the well depth where firing of the blast joints orblasting system should occur. This provides assurance that theelectronic blast control system and its downhole explosive system willbe properly located at a designed depth within the well bore before afiring control sequence can be initiated by the CPU.

Thus, at a designed depth within a well bore the temperature of the wellfluid, which will be directly representative of formation temperature,will have a known narrow range of temperature values. As a furthersafety feature, the electronic blast control system of this invention isprovided with a temperature sensor circuit 50 having the capability ofdetecting the temperature of the well fluid being produced from eachformation. This temperature sensor circuit has the capability of beingpreset with a narrow firing temperature range which will encompasscalculated or measured temperature at the predetermined firing depth ofthe downhole explosive system. When the fluid temperature being sensedis within the predetermined firing range, a logic output signal of thetemperature sensor will be conducted to the CPU for processing. As longas the temperature being sensed is within the firing range, the logicoutput signal received by the CPU will enable the CPU to output a firingsignal. If the temperature being sensed by circuit 50 is outside of thefiring temperature range, such as would occur if the electronic blastcontrol system is not located at designed well depth, the CPU willoutput a “safe” signal, thereby preventing initiation of the detonatorby the electrical energy of the battery 16. In order for the CPU tooutput a “firing” signal, the respective logic signals output by themotion sensor circuit, the clock timer circuit, the pressure sensor andthe temperature sensor must reflect positioning of the downhole blastingsystem at designed well depth and within a predetermined timing sequencein order for the downhole blasting system to fire. If the blastingsystem is not fired, or for some reason fails to fire, the tool isrendered safe for extraction from the well simply by permittingexpiration of the predetermined sequence that is programmed into theclock timer. Then, as the blast control system and its associatedblasting tool is moved toward the surface during extraction procedures,the other safety circuits will come into play.

The motion sensor circuit will detect upward motion of the tool and willchange its logic output signal to the “safe” mode, thereby preventingoutput of a firing signal by the CPU. Likewise, as the tool is moveduphole, the pressure sensor circuit and the temperature sensor circuitwill detect hydrostatic pressure and well fluid temperature that isoutside of the prescribed range for the firing sequence. These circuitswill then also change their respective logic output signals to the“safe” mode, thereby preventing the CPU from having a “firing” modeoutput signal that permits initiation of any of the detonators 38A-38Cby the electrical energy of the storage battery 30.

When two or more explosive energy devices are properly positioned withina wellbore or well casing it is desirable to prevent them fromsimultaneous firing; but rather to control their firing according to asequence. As shown in FIG. 3 an arming circuit is shown at 54 which maybe integrated with the CPU 42 or it may be provided as a separatecircuit. The arming circuit will permit only one of two or moredetonators to be fired at any given time. Firing of the lowermostdetonator 38C will cause an electronic arming signal or an explosivegenerated pressure pulse to actuate the arming circuit 54 and generatean arming logic signal to the next detonator 38B. Only then will thenext detonator be permitted to fire. Its firing will then stimulate thegeneration of an arming logic signal that arms the detonator circuit 38Aand permits its firing. Thus with the minimum cost of running multiplewell service tools into the well casing by means of a single wire linerun, multiple well service operations can be safely and efficientlycarried out.

Referring to FIG. 4, the storage battery 30 is incorporated within or iselectrically connected with a power supply circuit 56 that boosts thelow voltage, 15 volts for example, to a sufficiently high voltage, 144volts for example, for firing energization of an explosive chargedetonator. Detonator circuits 58, 60 and 62 are connected with the powersupply circuit and have diodes that are alternatively arranged toprovide positive or negative voltage as an additional level of safetyfor sequential firing of the detonators. Detonator circuit 58 has adiode 64 having its gate arranged to permit the flow of positive 144volt energy for firing energization of the detonator 38C. The detonator38B will not fire by positive voltage but will fire by negative voltage.The firing circuit 60 includes a diode 66 having its gate arranged topermit passage of negative voltage and block positive voltage. Thus whenpositive voltage is transmitted via circuit conductor 58 it will firedetonator 38C but will be blocked by diode 66 from also actuating thedetonator 38B. As mentioned above, and as a principal safety factor, thepositive electrical pulse of the power supply will only fire thelowermost detonator 38C since the upper and intermediate detonators willbe protected from firing by the exclusion feature of the arming circuit54. The diode 68 of detonator circuit 62 is arranged to pass onlypositive voltage for firing of the detonator circuit 38A.

As the electronic blast control is being run downhole, it is positionedfor firing and is fired, it is desirable to identify various downholeconditions of pressure and temperature for determination of formationconditions. It is also desirable to identify pressure and temperatureconditions immediately after firing as further evidence of formationconditions. These features are effectively provided for by theelectronic blast control system of the present invention whichincorporates a solid-state, non-volatile memory circuit 52, as shown inFIGS. 2 and 3, which continuously receives the output logic signals ofthe pressure and temperature circuits and also receives the outputsignals of the clock timer circuit 46 in order that the pressure andtemperature signals may be correlated with time. The data format of thememory circuit 52 is such that multiple thousands of sets of Delta time,temperature, and pressure are stored in the solid-state, non-volatilememory. After the electronic blast control system has been removed fromthe well, the memory circuit 52 is selectively coupled with the input ofa computer having a program and a memory adapted for receiving andprocessing the multiple data sets of the memory circuit. Thus, thecomputer can provide processed downhole data from the well, reflectingwell conditions before and after blasting as well as well conditions.This information may be plotted graphically or rendered by the computerin any suitable form that is desired for analysis.

With reference to FIG. 5 a timing sequence is shown in schematic form,based on a ten minute timing interval. However, it is to be borne inmind that the particular timing sequence that is shown is not to betaken as limiting the spirit and scope of the present invention, sincethe timing sequence can be variously arranged to suit the user. Belowthe timing sequence is shown the motion condition of the blast controlsystem of the present invention in relation to the timing sequence. Inminute 5 of the 10 minute interval of the timing sequence a programmedactivity can take place assuming the well service tool and its blastcontrol system is not in motion, which is the case that is shown in theschematic illustration. No blast control firing can occur during timingsegments 1, 3 and 7 since the motion of the instrument within thewellbore or well casing is received by the CPU and processed as a logicsignal that renders the instrument to its “safe mode”, preventing firingof the well service tool.

In view of the foregoing it is evident that the present invention is onewell adapted to attain all of the objects and features hereinabove setforth, together with other objects and features which are inherent inthe apparatus disclosed herein.

As will be readily apparent to those skilled in the art, the presentinvention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

1. A method for sequentially controlling the performance of work in anenvironment with a plurality of service mechanisms, comprising:selectively positioning a plurality of explosive actuated servicemechanisms in work performing arrangement and in serial fashion, each ofsaid service mechanisms having an electronically initiated explosivecharge; securing said electronically initiated explosive charge of eachof said service mechanisms against electronic initiation untilpredetermined individual safety parameters of each of said electroniccharge initiation circuits have been met; preparing an electronic chargeinitiation circuit connected with each of said electronically initiatedexplosive charges for passing a predetermined electronic voltage and forblocking a different electronic voltage; selectively applying apredetermined electronic voltage from a voltage source to a first ofsaid plurality of explosive actuated service mechanisms and initiatingthe explosive charge thereof and serially performing work ; andselectively applying a different electronic voltage from the voltagesource to a second of said plurality of explosive actuated servicemechanisms and initiating the explosive charge thereof and seriallyperforming additional work.
 2. The method of claim 1, comprising: saidpredetermined electronic voltage having a designated polarity energizingthe explosive charge of said first of said plurality of explosiveactuated service mechanisms and said different electronic voltage havingthe opposite polarity energizing the explosive charge of the second ofsaid plurality of explosive actuated service mechanisms.
 3. The methodof claim 1, comprising: one of said electronic charge initiationcircuits converting power supply voltage to a positive voltagerepresenting said predetermined electronic voltage and another of saidelectronic charge initiation circuits converting said power supplyvoltage to a negative voltage.
 4. The method of claim 3, comprising:said converting power supply voltage being applying battery voltage toselectively arranged diodes and yielding selective positive and negativevoltages; and stepping up battery supply voltage to explosive chargeinitiating voltage.
 5. The method of claim 1, comprising: running aservice tool into a well having a well casing, the service tool having aplurality of service sections being sufficiently spaced that explosiveenergization of said first of said plurality of explosive actuatedservice mechanisms will not render others of said plurality of explosiveactuated service mechanisms inoperable; said selectively applying apredetermined electronic voltage being controlling a battery type powersupply located on board said service tool and establishing gate circuitcontrolled positive and negative voltage outputs; and arming successiveexplosive actuated service mechanisms by detection of energy pulsescaused by energization of preceding explosive actuated servicemechanisms.
 6. The method of claim 5, comprising: said well service toolbeing a casing perforating assembly having a plurality of spacedserially arranged casing perforating guns each having a plurality ofelectronically initiated explosive shaped charges; establishingelectronic initiation of a first of said plurality of spaced seriallyarranged casing perforating guns from an on board battery supply by avoltage having a selected polarity; a second and subsequent casingperforating guns being disarmed during said running and positioning andbeing armed by an explosive generated pulse caused by energization ofthe explosive charges of said first of said plurality of spaced seriallyarranged casing perforating guns; and energizing said second andsubsequent casing perforation guns serially according to a programmedinitiation sequence and subject to programmed safety parameters.
 7. Acontrol system for controlling the sequential or serial performance ofwork in an environment, comprising: a service tool having a plurality ofspaced and serially arranged electronically initiated service mechanismseach having an explosive detonator being initiated by an electronicvoltage of selected polarity; an electronic controller system having acentral processing unit (CPU) and a power supply electronicallyconnected with said service tool and having selective positive andnegative voltage outputs, said CPU being programmable and establishingat least one safety parameter that must be met to arm said explosivedetonators for electronic initiation; a first of said spaced andserially arranged electronically initiated service mechanisms beingelectronically initiated by said CPU and initiating said explosivedetonator thereof with said electronic voltage of selected polarity, thedetonation thereof producing an energy pulse; and a second of saidspaced and serially arranged electronically initiated service mechanismshaving an arming circuit being normally unarmed and becoming armed uponsensing of the energy pulse, said second of said spaced and seriallyarranged electronically initiated service mechanisms beingelectronically initiated by said CPU and by an electronic voltage havingopposite polarity as compared with said selected polarity.
 8. Thecontrol system of claim 7, comprising: said environment being a wellhaving a casing; said plurality of spaced and serially arrangedelectronically initiated service mechanisms each being a casingperforation gun having an electronically energized explosive detonatorconnected for energization by said CPU; and said CPU having a solidstate non-volatile electronic memory adapted for input of safetyparameters including time, temperature, pressure and movement andproviding a firing signal when each of the safety parameters have beenmet, said firing signal initiating only the detonator of said firstcasing perforation gun, said second casing perforation gun having anunarmed state and being armed by a pulse signal transmitted to said CPUin response to detection of the energy pulse of detonation of the firstperforating gun, said CPU conducting a firing signal having a polarityopposite said selected polarity to said second casing perforation gunupon energy pulse responsive arming of the detonator of said secondperforation gun.
 9. The control system of claim 7, comprising: an energypulse sensor being coupled for energy pulse signal transmission to saidCPU upon firing the detonator of a first of said perforation guns; andsaid second of said perforation guns being in a disarmed state whenpositioned within the well and being armed by said CPU responsive totransmission of an energy pulse signal to said CPU to permit firing ofthe detonator thereof by a CPU controlled firing signal.